The present invention relates to a valve for detecting a liquid surface in a fuel tank, and the fuel tank to which the valve is attached, wherein an orifice partly facing an inside of the fuel tank and located at an upstream of a flow passageway for communicating between the fuel tank and a canister is closed by a valve member due to rising of the liquid surface.
For example, as disclosed in U.S. Pat. No. 5,028,244, a conventional valve for detecting the liquid surface is formed of a valve body having an orifice formed at an upper part thereof, a plurality of bottom through-holes formed at a bottom part thereof, and a plurality of peripheral wall through-holes formed at a peripheral wall; a valve member moving inside the valve body to open and close the orifice; and an urging member which can not close the orifice by moving the valve member against its own weight but which can close the orifice by moving the valve member in cooperation with buoyancy of the valve member.
A fuel tank provided with the valve for detecting the liquid surface as a full detecting valve and a cut valve is explained. In a normal condition, by an operation of a differential pressure valve communicating with both of the valves, communication between an inside of the fuel tank through the full detecting valve and the canister is shut off, and the inside of the fuel tank communicates with the canister through the cut valve.
Thus, fuel vapor in the fuel tank flows through the cut valve and the differential pressure valve into the canister.
When a cap is taken out to supply fuel into the fuel tank, a pressure inside the fuel tank is decreased to the atmosphere pressure, so that the differential pressure valve connects between the inside of the fuel tank and the canister through the full detecting valve, and cuts off the communication between the fuel tank and the canister through the cut valve.
Thus, when fuel is supplied by a fuel nozzle into the fuel tank, fuel vapor inside the fuel tank flows to the canister from the flow passageway through the bottom through-holes and the orifice, or through the peripheral wall through-holes.
Then, when the liquid surface of fuel rises and the valve member ascends in cooperation with its buoyancy and a force by the urging member, the valve member closes the orifice, so that the communication between the inside of the fuel tank and the canister is cut off.
When the orifice is closed as described above, the pressure inside the fuel tank is increased, and by detecting the increased pressure, controlling to stop supplying of fuel into the fuel tank can be done.
Also, when supplying of fuel into the fuel tank is finished, by the operation of the differential pressure valve, communication between the inside of the fuel tank and the canister through the full detecting valve is cut off, and the inside of the fuel tank communicates with the canister through the cut valve.
Incidentally, when the liquid surface of fuel descends from the full amount by using fuel, the valve member descends by its own weight against the urging force of the urging member, so that the orifice is opened.
In the aforementioned conventional valve for detecting the liquid surface, however, since a diameter of the orifice is set to be smaller than a diameter of the peripheral wall through-hole, in case foreign substances, such as dust, on the outer surface around the peripheral wall through-hole enter into the valve body together with the fuel vapor, the foreign substances entered into the valve body may clog the orifice.
Also, if the diameter of the peripheral wall through-hole is smaller than the diameter of the bottom through-hole, in case a part of the peripheral wall through-holes is soaked in fuel by swinging or moving of the automobile, the foreign substances entered together with the fuel vapor into the valve body through the peripheral wall through-holes may accumulate on the bottom part of the valve body.
The present invention has been made to solve the aforementioned problems, and it is an object of the present invention to provide a valve for detecting the liquid surface, wherein an orifice can not be clogged by foreign substances, the foreign substances can not accumulate on a bottom of a valve body, and a valve member can not be lifted by its force when fuel vapor flows out of the fuel tank.
Also, it is another object of the invention to provide a fuel tank, wherein an air passage resistance can not be increased by clogging of the peripheral wall through-holes due to the ascent of the liquid surface of fuel.